High surface area biocarbon monoliths for methane storage

New energy sources that reduce the volume of harmful gases such as SO_(x)and NO_(x)released into the atmosphere are in constant development.Natural gas,primarily made up of methane,is being widely used as one reliable energy source for heating and electricity generation due to its high combustion value.Currently,natural gas accounts for a large portion of electricity generation and chemical feedstock in manufacturing plastics and other commercially important organic chemicals.In the near future,natural gas will be widely used as a fuel for vehicles.Therefore,a practical storage device for its storage and transportation is very beneficial to the deployment of natural gas as an energy source for new technologies.In this tutorial review,biomaterials-based carbon monoliths(CMs),one kind of carbonaceous material,was reviewed as an adsorbent for natural gas(methane)adsorption and storage.

Preparation of activated carbon with low ash content and high specific surface area from coal in the presence of KOH

An activated carbon with ash content less than 10% and specific surface area more than 1 600 m 2 /g was prepared from coal and the effect of K containing compounds in preparation of coal based activated carbon was investigated in detail in this paper. KOH was used in co carbonization with coal, changes in graphitic crystallites in chars derived from carbonization of coal with and without KOH were analyzed by X ray diffraction (XRD) technique, activation rates of chars with different contents of K containing compounds were deduced, and resulting activated carbons were characterized by nitrogen adsorption isotherms at 77 K and iodine numbers. The results showed that the addition of KOH to the coal before carbonization can realize the intensive removal of inorganic matters from chars under mild conditions, especially the efficient removal of dispersive quartz, an extremely difficult separated mineral component in other processes else. Apart from this, KOH demonstrates a favorable effect in control over coal carbonization with the goal to form nongraphitizable isotropic carbon precursor, which is a necessary prerequisite for the formation and development of micro pores. However, the K containing compounds such as K 2 CO 3 and K 2 O remaining in chars after carbonization catalyze the reaction between carbon and steam in activation, which leads to the formation of macro pores. In the end an innovative method, in which KOH is added to coal before carbonization and K containing compounds are removed by acid washing after carbonization, was proposed for the synthesis of quality coal based activated carbon.

Highly reversible lead-carbon battery anode with lead grafting on thecarbon surface

A novel C/Pb composite has been successfully prepared by electmless plating to reduce the hydrogenevolution and achieve the high reversibility of the anode of lead-carbon battery （LCB）. The depositedlead on the surface of C/Pb composite was found to be uniform and adherent to carbon surface. Becauselead has been stuck on the surface of C/Pb composite, the embedded structure suppresses the hydrogenevolution of lead-carbon anode and strengthens the connection between carbon additive and sponge lead.Compared with the blank anode, the lead-carbon anode with C/Pb composite displays excellent charge-discharge reversibility, which is attributed to the good connection between carbon additives and leadthat has been stuck on the surface of C/Pb composite during the preparation process. The addition of CIPb composite maintains a solid anode structure with high specific surface area and power volume, andthereby, it plays a significant role in the highly reversible lead-carbon anode.

Experimental evaluation of activated carbon derived from South Africa discard coal for natural gas storage

Lacking in literature is the use of discard coal to produce activated carbon and in its subsequent use in the storage of natural gas. In this study, the characterization and gas storage evaluation of a largely porous activated carbon with large surface area synthesized from discard coal were investigated. Discard coals are waste material generated from coal beneficiation process. In developing the activated carbon, chemical activation route with the use of KOH reagent was applied. The effects of KOH/discard coal weight ratio (1:1, 2.5:1, 4:1), temperature (400-800 ℃) and particle size (0.15-0.25 mm, 0.25-0.5 mm, 0.5-1 mm) on the adsorptive properties of the activated carbon were methodically evaluated and optimized using response surface methodology. The synthesized activated carbon was characterized using BET, SEM/EDS, and XRD. The results showed that for each activation process, the surface area and pore volume of the resulting activated carbon increased with increased temperature and KOH/discard coal weight ratio. The maximum surface area of 1826.41 m2/g, pore volume of 1.252 cm^3/g and pore size of 2.77 nm were obtained at carbonization temperature of 800 ℃ and KOH/discard coal weight ratio of 4:1. Methane and nitrogen adsorption data at high pressure were fitted to Toth isotherm model with a predictive accuracy of about 99%. Adsorption parameters using the Toth model provides useful information in the design of adsorbed natural gas storage system. According to the requirements of adsorbent desired for natural gas storage, it could be stated that the synthesized activated carbon could well be applied for natural gas storage.

Effect of activated carbon and electrolyte on properties of supercapacitor

Effect of activated carbon and electrolyte on electrochemical properties of organic supercapacitor was investigated. The results show that specific surface area and mesoporosity of activated carbon influence specific capacitance. If specific surface area is larger and mesoporosity is higher, the specific capacitance will become bigger. Specific surface area influences resistance of carbon electrode and consequently influences power property and pore size distribution. If specific surface area is smaller and mesoporosity is higher, the power property will become better. Ash influences leakage current and electrochemical cycling stability. If ash content is lower, the performance will become better. The properties of supercapacitor highly depend on the electrolyte. The compatibility of electrolyte and activated carbon is a determining factor of supercapacitor’s working voltage. LiPF6/(EC+EMC+DMC) is inappropriate for double layer capacitor. MeEt3NPF4/PC has higher specific capacitance than Et4NPF4/PC because methyl’s electronegativity value is lower than ethyl and MeEt3N+ has more positive charges and stronger polarizability than Et4N+ when an ethyl is substituted by methyl.

Catalytic Pyrolyses of Rayon and the Effect on Activated Carbon Fiber

The catalytic pyrolyses of rayon have been studied respectively by thermo-gravimetric analysis (TGA) when rayon was treated with phosphoric acid (PA), three ammonium phosphate salts and ammonium sulfate (AS). The air is favorable to the catalysis of dibasic ammonium phosphate (DAP), but not to those of ADP, PA, AP, and AS obviously. It is put forward that a peak’s shape character can be described with the ratio of height to half-height-width (H/W /2) of the peak on a differential thermo-gravimetric (DTG) curve. A flat cracking peak, presenting a more moderate dehydration reaction, has a smaller ratio and could lead to higher carbonization and activation yields. The experimental results prove this view. According to expectation, the order of catalysis is: DAP≥ADP>PA> APAS no catalyst.

Optimal Electrochemical Performances of CO_2 Activated Carbon Aerogels for Supercapacitors

Activated carbon aerogels（ACAs） derived from sol-gel polycondensation of resorcinol （R） and formaldehyde （F） were pyrolyzed under Ar flow and activated in CO2 atmosphere. The morphology of ACAs was characterized by scanning electron microscopy （SEM） and the structural properties were determined by N2 adsorption at 77 K. The results show that ACAs have a typical three-dimensional nanonetwork structure composing of cross-linking of carbon nanoparticles. The specific surface area and the total pore volume remarkably increase with increasing activation time while the previous porous structure still remains. The specific capacitance of the 950-10-ACA electrode can reach up to 212.3 F/g in 6 mol/L KOH electrolyte. The results of constant-current charge-discharge testing indicate that the ACAs electrodes present fast charge- discharge rate and long cycle life （about 98% capacitance retained after 3000 charge-discharge cycles at 1.25 mA/cm2）. Lower internal resistances can be achieved for 950-10-ACA electrode in KOH electrolyte. Our investigations are very important to improve the wettability and electrochemical performance of electrode for supercapacitors.

Enhanced Capacitive Characteristics of Activated Carbon by Secondary Activation

The effect of the improvement of commercial activated carbon(AC) on its specific capacitance and high rate capability of double layer(dl) charging/discharging process has been studied. The improvement of AC was carried out \%via\% a secondary activation under steam in the presence of catalyst NiCl\-2, and the suitable condition was found to be a heat treatment at about 875 ℃ for 1 h. Under those conditions, the discharge specific capacitance of the improved AC increases up to 53.67 F/g, showing an increase of about 25% as compared with that of as-received AC. The good rectangular-shaped voltammograms and A.C. impedance spectra prove that the high rate capability of the capacitor made of the improved AC is enhanced significantly. The capacitance resistance(RC) time constant of the capacitor containing the improved AC is 1\^74 s, which is much lower than that of the one containing as-received AC(an RC value of 4.73 s). It is noted that both kinds of AC samples show a similar specific surface area and pore size distribution, but some changes have taken place in the carbon surface groups, especially a decrease in the concentration of surface carbonyl groups after the improvement, which have been verified by means of X-photoelectron spectroscopy. Accordingly, it is suggested that the decrease in the concentration of surface carbonyl groups for the improved AC is beneficial to the organic electrolyte ion penetrating into the pores, thus leading to the increase in both the specific capacitance and high rate capability of the supercapacitor.

Removal of Dyes from Wastewater by Adsorption onto Activated Carbon: Mini Review

Nowadays, wastewater from dyeing industries became a challenging issue in the world. Researchers have reported several techniques to treat those effluents based on their projects. Adsorption is the most common method because of cheap, simple and effective method. In this work, activated carbon was used for dye adsorption purpose. This adsorbent has high surface area and high porosity to remove dye. This review highlighted some important results of the last few years regarding the use of activated carbon in wastewater treatment. Research findings supported that adsorption process is spontaneous in nature. Adsorption data confirmed Langmuir model, indicating the chemisorption occurred.

A new preparation process of coal-based magnetically activated carbon

Fe/C-based magnetically activated carbon(MAC) was obtained by carbonizing and activating its precursor, that was prepared by co-precipitation of anthracite coal impregnated in ferric chloride solution. The effect of the concentrations of FeCl3 and pH of solution on BET surface area, pore volume and magnetic properties of the MAC was studied by BET N2 adsorption and VSM method. The results indicated that the magnetization of MAC gradually increases with increasing concentration of FeCl3 and pH value of solution, and BET surface area was inclined to fluctuation. The largest BET surface area and magnetization of MAC were 1327.5 m2/g and 35.56 emu/g, respectively. The form of magnetic matter in the magnetically activated carbon was mainly Fe3C by X-ray powder diffraction(XRD) and magnetic attraction test.

A comparative study of the pore characteristics and phenol adsorption performance of activated carbons prepared from oil-palm shell wastes by steam and combined steam-chemical activation

Oil-palm shell wastes were successfully converted into useful activated carbons in a systematic and novel approach by optimizing the pyrolysis conditions and subsequent steam activation conditions to maximize the BET surface area.The optimal activation conditions were a steam flow rate of 1.13 kg/h,hold time of 1.5 h and temperature of 950℃,yielding BET areas of 1432.94 and 1382.95 m^(2)/g for nitrogen-pyrolyzed and vacuumpyrolyzed chars,respectively.In steam-chemical activation,one-step activation of oil-palm shell in steam with potassium carbonate(K_(2)CO_(3)),sodium carbonate(Na_(2)CO_(3))or potassium chloride(KCl)was conducted,resulting in BET area output order of shell/K_(2)CO_(3)(710.56 m^(2)/g)>shell/KCl(498.55 m^(2)/g)>shell(366.7 m^(2)/g)>shell/Na_(2)CO_(3)(326.62 m^(2)/g).This study reported the first use of KCl and Na_(2)CO_(3)as chemical reagents in one-step steam-chemical activation of biomass.KCl-activated carbon exhibited retardation of tar formation property,resulting in better pore development than pure steam activated carbon.Phenol adsorption of activated carbon is not only a function of the BET surface area but also the type of pyrolysis used prior to physical activation.Activated carbon(BET area of 1192.29 m^(2)/g)pyrolyzed under vacuum could adsorb 87%more phenol than that pyrolyzed in nitrogen flow which had a higher BET area of 1432.94 m^(2)/g.Phenol adsorption capacities of activated carbons are:shell pyrolyzed under vacuum(275.5 mg/g)>shell pyrolyzed in N_(2)flow(147.1 mg/g)>shell/K_(2)CO_(3)(145.7 mg/g)>shell without pyrolysis(12.1 mg/g).These activated carbons would be highly suitable in industry processes to remove phenolic contaminants.

Electrochemical Impedance Spectroscopy Study on Novel Carbon-Sulfur Nano-Composite Cathodes in Lithium Rechargeable Batteries

Carbon-sulfur nano-composite cathodes for lithium rechargeable batteries were investigated by electrochemical impedance spectroscopy (EIS). The novel carbon-sulfur nano-composite material was synthesized by heating sublimed sulfur and high surface area activated carbon (HSAAC) in certain conditions. Equivalent circuits were used to fit the spectra at different discharge states. The variations of impedance spectra, charge-transfer resistance and double layer capacitance were discussed. The changes of EIS with potential were analyzed based on a plausible electrical equivalent circuit model, and some parameters were measured and analyzed about electrochemical performance and state of charge and discharge of the electrode. The good accuracy in fitting values of the model to the experimental data indicates that the mathematical model gives out a satisfying description upon the mechanism of high rate of capacity fade in lithium-sulfur battery.

Impact of hydrolysis on surface area and energy storage applications of activated carbons produced from corn fiber and soy hulls

Complete utilization of lignocellulosic biomass through the creation of value-added coproducts is one of the key strategies of the Bioenergy Technologies Office(BETO)for the cost-effective production of biofuels and biochemicals.A green approach to producing lightweight and high specific surface area(SSA)activated carbons(ACs)from sustainable biomass sources is of great interest to producers and users of energy devices such as batteries and supercapacitors.While direct conversion from biomass has been studied extensively,AC with relatively high surface areas can be produced more cost-effectively when leveraged as a co-product from a biorefinery.In this paper,we discuss the production of high specific surface area activated carbons from residual fiber(fiber remaining after extraction of C5-sugars)generated as part of a C5 biorefinery.The surface,morphological characteristics using SEM and TEM,and energy storage behavior of ACs produced using the C5 extracted residual fiber were evaluated in the present study.The ACs produced from the residual fiber delivered an order of magnitude higher surface area than the one directly from corn pericarp fiber and soy hulls.The surface area of the ACs produced from pre-hydrolysis DDG was only 10 m^(2)/g compared to 689 m^(2)/g for soy hulls whereas after hydrolysis these values increased significantly(DDG:1700 m^(2)/g and soy hulls:1300 m^(2)/g).TEM images indicated high exfoliation,explaining the change in surface area values.Under the same current density(500 mA/g)the cycling performance of the ACs increased as the surface area increased significantly.

One-step synthesis of robust carbon nanotube foams with ultrahigh surface area for high-performance lithium ion battery

A novel three-dimensional(3D) carbon nanotube foams(CNTF) with ultrahigh specific surface area have been fabricated through a unique but facile one-step synthesis by using CO_2 as both carbon source and activating agent. The activation temperature and time have been adjusted, and the best sample demonstrates a specific surface area of 1959.8 m^2 g^(–1) and a total pore volume of 3.23 cm^3 g^(–1). A reversible capacity of about 870 mAhg^(–1) is maintained at 50 mAg^(–1) when the CNTF used as cathode materials. Meanwhile, the capacity is as large as 320 mAhg^(–1) at the current density of 2 A g^(–1) and the capacity retention is nearly 100% after 500 cycles. These excellent and highly stable battery performances should be attributed to the structural advantages of as-synthesized CNTFs generated by using a facile CO_2-assisted strategy, which may potentially be applied in large scale production of porous 3D carbon materials in the fields of energy storage and conversion.

Adsorption of naphthalene onto a high-surface-area carbon from waste ion exchange resin

A high-surface-area carbon （KC-1） was prepared from waste polystyrene-based ion exchange resin by KOH activation and used for naphthalene adsorption. The carbon exhibited a good hydrophobic nature with developed porous structure, favoring the adsorption of organic compounds. The Brunauer-Emmett-Teller surface area and total pore volume of KC- 1 were 3442.2 and 1.68 cm3/g, respectively, which can be compared with those of KOH-activated carbons prepared from other precursors. Batch experiments were carded out to investigate the adsorption of naphthalene onto KC-1. The equilibrium data were analyzed by the Langmuir, Freundlich, and Polanyi- Manes isotherms and agreed with the Polanyi-Manes Model. The adsorption of naphthalene depended greatly on the porosity of the carbon, and the dispersive interactions between naphthalene and carbon could be relatively weak. The pH variation in aqueous solution had little effect on the adsorption process. The equilibrium time for 0.04 g/L of carbon dose was around 5 hr. Different models were used to evaluate the kinetic data and the pseudo second-order model was suitable to describe the kinetic process of naphthalene adsorption onto KC-1. Regeneration of spent carbon could be carded out effectively by alcohol treatment. The results indicated that KC-1 was a promising adsorbent for the removal of polycyclic aromatic hydrocarbons from aqueous solutions.

稻草秸秆-煤基压块活性炭的制备及工艺优化

为降低压块破碎活性炭的制备成本,以稻草秸秆炭和大同不黏煤为主要原料,利用配煤工艺,经过成型、炭化、H_(2)O_((g))-CO_(2)联合活化成型炭制备压块破碎活性炭。采用碘吸附法、亚甲蓝吸附法以及BET、FTIR和Boehm滴定方法测试和表征不同条件下制备的压块破碎活性炭。实验结果表明,加入适量稻草秸秆炭和H_(2)O_((g))-CO_(2)联合活化对活性炭的碘吸附值和亚甲蓝吸附值均有明显提升作用。Boehm滴定结果表明,活性炭具有丰富的酸性和碱性官能团。当活化温度为900℃、活化时间为2.5 h、H_(2)O_((g))和CO_(2)流量比为2时,制备的活性炭的碘吸附值、亚甲蓝吸附值和比表面积分别达到790 mg/g、262 mg/g和809 m^(2)/g。

Breakthrough CO_2 adsorption in bio-based activated carbons

In this work, the effects of different methods of activation on CO2 adsorption performance of activated carbon were studied. Activated carbons were prepared from biochar, obtained from fast pyrolysis of white wood, using three different activation methods of steam activation, CO2 activation and Potassium hydroxide（KOH） activation. CO2 adsorption behavior of the produced activated carbons was studied in a fixed-bed reactor set-up at atmospheric pressure, temperature range of 25–65°C and inlet CO2 concentration range of10–30 mol% in He to determine the effects of the surface area, porosity and surface chemistry on adsorption capacity of the samples. Characterization of the micropore and mesopore texture was carried out using N2 and CO2 adsorption at 77 and 273 K, respectively.Central composite design was used to evaluate the combined effects of temperature and concentration of CO2 on the adsorption behavior of the adsorbents. The KOH activated carbon with a total micropore volume of 0.62 cm3/g and surface area of 1400 m2/g had the highest CO2 adsorption capacity of 1.8 mol/kg due to its microporous structure and high surface area under the optimized experimental conditions of 30 mol% CO2 and 25°C. The performance of the adsorbents in multi-cyclic adsorption process was also assessed and the adsorption capacity of KOH and CO2 activated carbons remained remarkably stable after50 cycles with low temperature（160°C） regeneration.

High Power Density Electric Double Layer Capacitor with Improved Activated Carbon

The improvement on commercial activated carbon (AC) through the reactivation under steam in the presence of NiCh(2) catalyst leads to the increases of both energy mid power densities of electric double layer (dl) capacitors. When AC was treated at 875 V for 1 h, its discharge specific Capacitance increases up to 53.67 F (.) g(-1), an increase of about 25% compared to the as-received AC. Moreover, a significaut increase in high rate capability of electric dl Capacitor was found after the improvements. Surprisingly, both the treated and untreated AC samples showed similar specific surface area and pore size distribution, but some changes in the surface groups and thew concentrations after reactivation were verified by X-photoelectron spectra. Thus, it is reasonable to conclude that the decrease in the surface concentration of the carbonyl-containing species for the improved AC results in an increase of accessibility of the pores to the organic electrolyte ion, causing the enhancements of both the specific capacitance and high rate capability.

有机胺改性树脂基球形活性炭对二氧化碳的吸附行为

以球形结构的固废离子交换树脂为原料,经CO_(2)活化、酸洗处理制得具有较高比表面积和较大中孔孔容的树脂基球形活性炭(HRSAC),然后在其表面负载聚乙烯亚胺(PEI)制得吸附材料PEI-HRSAC。系统考察了PEI负载量和吸附温度对CO_(2)吸附性能的影响,结果表明,在活化温度为950℃、活化时间为1 h的最佳活化工艺条件下,所制得的树脂基球形活性炭经酸洗处理后其比表面积为1365 m^(2)/g,中孔孔容为2.04 cm^(3)/g,中孔孔径主要分布在10~40 nm;PEI-HRSAC吸附材料对CO_(2)的吸附性能随吸附温度和PEI负载量的升高先增大后减小;当PEI负载量为65%、吸附温度为75℃时,PEI-HRSAC吸附材料对CO_(2)的吸附量最高,约为4.09 mmol/g,在经过4次循环吸/脱附后吸附量仍保持在较高水平(3.66 mmol/g)。

活性炭负载锌催化剂的制备及其处理煤化工废水的试验研究

为实现煤化工高盐废水水质处理效能的提升,以宁夏生产的煤制活性炭为载体,采用直接浸渍法、沉淀-煅烧法2种负载方法,选取Zn元素作为催化剂的活性组分,制备了用于臭氧氧化降解工艺用催化剂,考察了催化剂对宁夏宁东地区煤化工高盐废水中COD去除情况的探究。结果表明:将活性炭与浓度为0.4 mol/L的氯化锌溶液按照m(活性炭)∶V(溶液)=1∶3的比例混合,完全沉淀后,在氮气环境保护下,在恒定300℃的温度下煅烧2 h,制得活性组分为氧化锌的ZnO/AC催化剂,其比表面积为1063.45 m2/g,COD去除率高达71.7%,处理后废水中Zn^(2+)质量浓度增加99.8882 mg/L,高比表面积有利于发挥物理吸附与化学催化的协同作用,提高活性炭基催化剂的催化性能。该臭氧催化剂催化效果显著,可用于煤化工高盐废水中有机物的去除。